I love Samuel, Theodore and Genevieve, and Sam, Theo and Nevie are just adorable as nicknames! However, if you're asking about middle names too, I personally am not a huge fan of the name Pearl, and it slightly seems to me that it lacks the classic feel of your boy middle names. If you want to keep with the one syllable theme (which I love), GenevieveMay or GenevieveMaud/e comes to mind, but I particularly like GenevieveClaire - feel free to ignore me regarding Pearl though as it all comes down to what you love anyway. Good luck!